1. Field of the Invention
The present invention relates to a liquid ejection head, a method of manufacturing a liquid ejection head, and an image forming apparatus, and more particularly to a liquid ejection head in which a piezoelectric layer is provided between two electrode film layers, a method of manufacturing the liquid ejection head and an image forming apparatus equipped with the liquid ejection head.
2. Description of the Related Art
Japanese Patent Application Publication No. 2006-150948 (for example, paragraphs [0010], [0028] and [0038]) discloses a piezoelectric actuator comprising an individual electrode formed so as to surround the central portion of a pressure chamber, in a region which overlaps with the marginal portion of the pressure chamber apart from the central portion when observed in plan view. Moreover, Japanese Patent Application Publication No. 2006-150948 also describes increasing the amount of displacement of a diaphragm by using a ring-shaped individual electrode and adopting a structure in which a piezoelectric layer is not provided in the region which overlaps with the central portion of the pressure chamber.
International publication No. WO 92/08617 discloses that a single continuous electrode is arranged on a first surface of a plate-shaped piezoelectric converter segment, and first and second electrode rows arranged alternately and spaced apart in a mutually interlocking fashion are arranged on a second surface, the continuous electrode and the first electrodes being connected to a ground potential and the second electrode being connected to a positive potential.
In recent years, increase in the density of nozzles in a liquid ejection head has been progressing and there have been demands to achieve increased density of the nozzle arrangement (reduction in the surface area of piezoelectric actuators) at the same time as increasing the amount of displacement of the diaphragm by the piezoelectric actuators.
However, if the piezoelectric layer which covers the diaphragm is cut away completely as in Japanese Patent Application Publication No. 2006-150948, although the amount of displacement of the piezoelectric actuator can be increased, the rigidity of the diaphragm is diminished. If the rigidity of the diaphragm is low, then it becomes difficult, for example, to eject liquid of high viscosity and therefore piezoelectric actuators having a larger amount of displacement and greater rigidity are sought.
International publication No. WO 92/08617 aims to increase the amount of displacement by means of an elongating deformation effect between electrodes of different potential, but since the electrode shape is complex, it is difficult to lay out connections for the plurality of wires. Therefore, in the composition described in International publication No. WO 92/08617, it is difficult to create piezoelectric actuators having high density.